This project will examine how children develop the ability to rapidly interpret speech as it is being heard. To accomplish this research objective, a free-head eyetracking system will be used to monitor the eye movements of children (ages 4 years and up) as they respond to spoken instructions. By examining which objects a child considers as he or she is listening to speech, certain inferences can be made about the on-going processes that underlie language comprehension. Of particular interest is how the child interprets sentences that contain uncertainties or ambiguities regarding the grammatical relationships between words and phrases. Prior research has found that adults rapidly commit to a single interpretation of an ambiguous phrase by coordinating several key sources of information, including detailed knowledge of individual words, information from the prosody ("melody") of speech, and information from the situation or context. The current research examines how a child develops this rapid and relatively interactive processing system. By testing the child's ability to take advantage of these potentially useful sources of information, we can gain a better understanding of how language is represented, organized, and processed by the normally developing child. Answering questions about children's language processing abilities has long eluded researchers, primarily because of technical limitations on tests suitable to use with children. The free-head eyetracking technology provides a new window into on-going language interpretation, supplying insights into normal development that have potential applications to the treatment of language-developmental delays and pathologies.